In the current chapter, the control of nonmetallic inclusions in an ultralow carbon Al-killed Interstitial Free (IF) steel produced by the route of hot metal pretreatment → converter steelmaking → RH refining → continuous casting was introduced. The variation in the composition of ladle slag throughout the production process, the morphology, and number density of non-metallic inclusions in the steel at the entire process were investigated through industrial trials and laboratory detection. Key issues in the control of non-metallic inclusions during IF steel production were summarized.